A variety of ungelled epoxy-amine reaction products are known. For example, U.S. Pat. No. 2,651,589 describes preformed reaction products between a glycidyl ether having a 1,2-epoxy equivalency of greater than one and a hardening agent, e.g., polyamines such as ethylenediamine or diethylenetriamine. However, Example 6 of this patent, illustrates the gelation difficulties well recognized in the art when the reaction involves only one-half mole of a polyamine hardening agent present for each epoxy equivalent. To avoid gelation, such preformed reaction products preferably include one mole of hardening agent, e.g., polyamine, per epoxy equivalent, optionally, as little as 0.9 mole of hardening agent per epoxy equivalent. In a similar fashion, a standard procedure throughout the art in the formation of ungelled polyamine-polyepoxide reaction products is to utilize excess polyamine, i.e., at least two moles of polyamine per epoxide equivalent, followed by stripping off excess amine after completion of the reaction (see, e.g., U.S. Pat. Nos. 2,909,448; 3,129,133; and 4,116,900).
Some ungelled polyamine-polyepoxide reaction products have been utilized in the area of cationic electrodeposition. Such products have included ungelled polyamine-polyepoxide reaction products as described above, further reacted with a monoepoxide or a monocarboxylic acid and with all or part of the amine groups neutralized with a water-soluble acid (see, e.g., U.S. Pat. No. 4,116,900). Other ungelled polyamine-polyepoxide reaction products utilize polyoxyalkylene-polyamines as the polyamine (see, e.g., U.S. Pat. Nos. 3,963,663 and 4,423,166).
In contrast to the prior art, the ungelled thermoplastic resins of the present invention are essentially devoid of oxyalkylene moieties and are formed from admixtures having equivalent ratios of polyamine to polyepoxide which would previously have been considered to yield a gelled product.